Jobs → Engineering → Senior Backend Engineer

About the Role We are looking for a Senior Backend Engineer to join Koinworx in the Netherlands. This role requires 8+ years of experience and focuses on building scalable backend systems using C#/.NET. Key Responsibilities • Design and implement RESTful APIs and GraphQL services • Develop and maintain microservices architecture • Integrate with third-party APIs and handle service failures • Implement security best practices and graceful failure handling • Lead code reviews and ensure code quality • Collaborate with product team on technical requirements • Optimize performance and maintainability of existing codebases Requirements • 8+ years of experience in backend development with C#/.NET • Expertise in ASP.NET Core MVC, REST APIs, and API versioning • Experience with Dependency Injection, Middleware, JWT, OAuth/OIDC • Hands-on experience with HttpClientFactory, Polly, and third-party API integrations • Experience with unit and integration testing using xUnit, NSubstitute • Knowledge of AWS services including ECS Fargate, Lambda, SQS/SNS, DynamoDB • Experience with Terraform, GitLab CI/CD, and AWS Secrets Manager • Understanding of Server-Driven UI, Backend-for-Frontend, and modular architecture • Strong collaboration, communication, and technical decision-making skills